A dose of the measles, mumps and rubella (MMR) vaccine is seen at a health center in Lubbock, Texas, on February 27, 2025 (AFP / RONALDO SCHEMIDT)
"Every year, 5,700 U.S. children suffer seizures from the measles, mumps and rubella (MMR) vaccine. There is a five-fold higher risk of seizures from the MMR vaccine than seizures from measles infection," says a March 4, 2025, Facebook post from an Ontario, Canada-based alternative education company called Collective Evolution.
"In the U.S., measles is generally a benign, short-term viral infection; 99.99% of measles cases experience full recovery," it continues.
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Screenshot from Facebook taken March 19, 2025
The same claim has circulated elsewhere on Facebook and other platforms such as Instagram, Threads, X and Telegram -- including in Portuguese, Vietnamese, Norwegian, Danish and Bengali.
Measles is a highly infectious illness that usually causes a high fever, cough and rash. However, it can trigger more serious conditions like pneumonia, blindness and encephalitis-related brain swelling, which can lead to severe seizures and neurological damage (archived here).
US health authorities recommend that children receive one shot of the MMR vaccine between 12 and 15 months of age and a second shot between four and six years old (archived here). Canada has issued similar guidance (archived here).
The United States effectively eradicated measles in 2000, thanks largely to the country's vaccination and virus control programs, but falling vaccination rates have left some populations vulnerable (archived here).
Two unvaccinated people died in the US states of Texas and New Mexico amid a recent measles outbreak. In 2025, there had been more than 300 confirmed cases reported across 14 states as of March 13.
Data published by the US Centers for Disease Control and Prevention March 14 indicated that about 95 percent of the infections were in unvaccinated individuals, while another three percent impacted people who had only received one MMR vaccine dose (archived here).
"If too many children are non-immune to measles, there will be an outbreak eventually in the community. Many children will be hospitalized and some will have permanent complications or die," said Christina Hermos, a pediatric infectious disease physician at UMass Memorial Medical Center (archived here).
"This has already happened in Texas and it will happen again if the vaccination rates drop," Hermos said in a March 20 email.
'Like comparing apples to a zebra'
The MMR vaccine -- and the measles, mumps, rubella and varicella (MMRV) shot that also inoculates against varicella, or chickenpox -- is associated with a small increased risk of febrile seizures, or convulsions in children that are caused by a fever.
A common adverse event following vaccination is temporary fever, and the CDC estimates that in one out of every 3-4,000 children under the age of seven this can lead to a febrile seizure (archived here and here).
However, febrile seizures do not have long-lasting health effects.
On the other hand, about one in every 1,000 people who contract the measles virus can develop encephalitis, which can cause irritation and swelling in the brain (archived here).
Primary measles encephalitis, as this condition is called, can cause seizures and other neurological symptoms (archived here). An estimated 25 percent of patients with primary measles encephalitis suffer permanent brain damage, and between 10 and 15 percent of children who acquire it die, according to the nonprofit Encephalitis International.
Another rare measles-induced condition called subacute sclerosing panencephalitis (SSPE) can also cause severe neurological symptoms, including seizures (archived here). There is no cure or effective treatment for SSPE, and most patients die within five years of their diagnosis.
Hermos said measles infection poses a much greater risk of harmful seizures.
While only a small percentage of those who contract measles will develop some form of encephalitis, she said it can cause death and permanent development delays in addition to other serious complications such as pneumonia or permanent hearing loss.
Erica Prochaska, a pediatric infectious disease specialist at Johns Hopkins Children's Center, also pointed to the difference between febrile seizures, which are not uncommon in young children, and potential brain damage from encephalitis, which can have lifelong effects (archived here).
"It's not even like comparing apples and oranges. It's like comparing apples to a zebra, for example, just in how different the processes are," she said March 17.
Prochaska also said there is a slightly higher risk of febrile seizures for children who receive the MMRV vaccine versus the MMR vaccine, so some pediatricians will recommend receiving the varicella vaccination in a separate shot. But she said both vaccination types are safe, and that they are the best tools to ward off the measles virus (archived here).
"As a pediatrician, an infectious diseases doctor and a parent, I rely on vaccines like measles, mumps and rubella to protect my patients and my own children," she said.
AFP has debunked other false claims about vaccines here.